In reviewing the performance characteristics of a commercial light duty liquid dishwashing composition--an unbuilt liquid detergent--based upon a mixture of an alkyl benzene sulfonate detergent, an alkyl ethenoxy ether sulfate detergent and an alkanoic acid alkanolamide foam booster, it was noted that this liquid exhibited shortcomings in grease soil removal and in the emulsification of grease soil at temperatures in the range of 18.degree. C. to 26.degree. C.
It has now been discovered that the shortcomings described above can be overcome by including in the described compositions a source of magnesium ions and a source of triethanolammonium ions provided that the weight ratio of magnesium ions to triethanolammonium ions is in the range of about 2:1 to about 1:2.4 and further provided that the concentration of magnesium ions is at least about 0.5% by weight of the liquid detergent composition.
The discovery that the use of controlled proportions of magnesium ion and triethanolammonium ion imparts improved oily soil removal and oily soil emulsification characteristics to the claimed liquid detergent compositions is surprising. More particularly, it was noted that the improvement in oily soil removal and in oily soil emulsification provided by magnesium ion in the absence of triethanolammonium ion tends to diminish at concentrations above at least about 0.5% of magnesium ion in the liquid detergent composition. Further, it was noted that triethanolammonium ions exhibit little or no improvement in oily soil removal or oily soil emulsification in the absence of magnesium ions. Thus, it is considered that the improved grease soil removal and emulsification properties achieved by the joint use of controlled proportions of magnesium ions and triethanolammonium ions clearly is unexpected and suggests that synergism or co-action is present. Furthermore, the proportions are different than the proportions taught in U.S. Pat. No. 4,435,317 which are based on the concentration of C.sub.10 -C.sub.16 alkyl sulfate.
In further aspects of this invention, it was discovered that optimum proportions for enhanced grease emulsification, particularly at concentrations of magnesium ion in the range of about 0.5% to 1% by weight of magnesium ion is in the range of about 1:2, e.g., about 1:1.4 to about 1:2.4, of magnesium ion to triethanolammonium ion. However, from the standpoint of optimum grease soil removal at 18.degree. C. to 26.degree. C., the optimum ratio of magnesium ion to triethanolammonium ion is about 1:1 at concentrations of magnesium ion in the range of about 1% to 1.8% by weight where the concentration of the liquid detergent composition is about 3% by weight.